The removal of various types of cables from conduits is a common practice, especially when the cables have been employed in the conduit for many years. The removal of the cables is often necessary to upgrade and improve systems which use electrical cables in them. Recabling is common in the refurbishment of electrical and communication systems. In such refurbishment, for both practical and economic reasons, the new cables are often installed in existing conduits. To get the new cable in, the old cable must be pulled out.
In theory, the removal of old cable from a conduit should be straight forward. If the cable could be pulled in to begin with it should be possible to pull it back out. However, a high coefficient of friction of the cable in the conduit can exist since the old soap or wax lubricants used to install the cable will be long gone or hardened. If the tension required to remove the cable from the conduit is more than the tensile strength of the conductors, the cable wires will break and removal of the cable from the conduit will not be completed without drastic measures such as breaking into the conduit, often requiring removal of a wall, digging up the ground, etc.
In lubricating the interface between two relatively moving cable and conduit surfaces a number of requirements must be met. The lubricant must be essentially chemically and physically inert with respect to the surfaces. The lubricant must reduce the force required to move one surface over the other and the lubricant must be in a form that permits the easy application of the lubricant to one or both surfaces. Examples of lubricants particularly useful in installing cable into a conduit are disclosed in U.S. Pat. Nos. 4,461,712, 4,522,733 and 4,781,847 which are aqueous based lubricants.
Lubricants lower the coefficient of friction of the cable jacket against the conduit wall, which lowers the tension required to remove or pull out the cable. However, pulling tension is not the only problem in removing old cable from a conduit. Often the cable is adhered or cemented (commonly termed "frozen") to the conduit by dried wax or soap lubricants, silt, rust, or exuded bitumen. While this bonding is discontinuous and weak, it can still require enormous force to initially move the cable because it is necessary to shear the whole length of the adhesive bond. This adhesion can require a force great enough that the cable wires break rather than pull away from the conduit. Prior cable lubricants do not dissolve the cable bonding agents which are present in many conduits having old cable.
Therefore, a need exists for a loosening composition that can be easily handled, easily applied, and easily cleaned, which provides effective lubricating and solvating properties for binding agents in a conduit having a cable, allowing for easy removal of the cable from the conduit.